Misalignment inspection of multilayer PCBs with an automated X-ray machine vision system

In recent times, multilayer printed circuit boards (PCBs) have been extensively applied in the electronics industry owing to their high capacities for complex and densely packed circuit layouts arranged in a limited space. The inspection of fabricated multilayer PCBs is thus important in order to ensure quality control and improve the fabrication process. In this paper, an automated X-ray machine vision system was developed exclusively for the inspection of the layer-to-layer misalignment of laminated multilayer PCBs. Based on a mechatronics system and X-ray image processing techniques, an automated misalignment inspection process was established. Experiments meant to inspect three critical layer-to-layer misalignment modes, expansion, contraction, and offset, found within ten-layer PCB samples, were conducted to test the feasibility of the developed machine inspection system. The experimental results show that the developed X-ray machine vision system, combined with the automated misalignment inspection process, was able to undertake misalignment inspection of certain multilayer PCBs.